The present embodiments relate generally to apparatus and methods for treating medical conditions, and more specifically, to stent-grafts for use in body vessels to treat those medical conditions.
Stents may be inserted into an anatomical vessel or duct for various purposes. Stents may maintain or restore patency in a formerly blocked or constricted passageway, for example, following a balloon angioplasty procedure. Other stents may be used for different procedures, for example, stents placed in or about a graft have been used to hold the graft in an open configuration to treat an aneurysm. Additionally, stents coupled to one or both ends of a graft may extend proximally or distally away from the graft to engage a healthy portion of a vessel wall away from a diseased portion of an aneurysm to provide endovascular graft fixation.
Stents may be either self-expanding or balloon-expandable, or they can have characteristics of both types of stents. Self-expanding stents may be delivered to a target site in a compressed configuration and subsequently expanded by removing a delivery sheath, removing trigger wires and/or releasing diameter reducing ties. With self-expanding stents, the stents expand primarily based on their own expansive force without the need for further mechanical expansion. In a stent made of a shape-memory alloy such as nitinol, the shape-memory alloy may be employed to cause the stent to return to a predetermined configuration upon removal of the sheath or other device maintaining the stent in its predeployment configuration.
If stents are coupled to a graft, sutures are commonly threaded between a portion of the stent and the graft to provide a secure engagement. If multiple sutures are provided, safety may be increased in the event a suture breaks. However, the provision of multiple sutures can increase the overall amount of material used, which may arise in a larger profile when compressed in the delivery configuration. A larger delivery profile may reduce the overall number of patients who can be treated with such stent-grafts.